Mac (10.5 and later) with Android (3.0 and later): Plug an Android into a Windows or Linux machine, turn on disk mode, and your phone is basically a drive. Plug into a Mac, and you get a warning. Google's own utility fixes that.

The big "if" clause is that you have a device that's running at least Android 3.0 or above (meaning "Honeycomb," "Ice Cream Sandwich," or the just-out "Jelly Bean."). That's about 13.3 percent, as of this writing. But for those who are, and for those due to arrive soon, Google's own Android File Transfer utility is a simple, useful app for transferring files between your Android storage and the Mac. Media sync apps like doubleTwist and other Mac/Android solutions involve far less click-and-explore, but for those wanting simple access to pictures, music, and files, this is the best option. Install the app, and whenever you plug in an Android phone over USB, the app window will open, and interact properly with your Mac's own Finder windows.